You're probably too focused in on hashes initially. The best way to start is to do some research on data structures, then decide how to structure your address book in a more abstract manner. Once this is done it would be easier to see how you could use hashes to implement this project.

An address book actually is a good project for learning how to structure data, since you can start with a basic flat list and evolve it into an arbitrarily complex contact management system. This could give you the opportunity to play with a variety of data structures.